1. Field of the Invention
The present invention relates to an ink jet printer having an exchangable printing head.
2. Description of Related Art
A known ink jet printer includes a carriage, which can reciprocate horizontally along a printing medium. A head holder is mounted removably on the carriage, and supports print heads on it. The heads can eject ink onto the medium. The printer also includes a capping device, which includes protective caps for covering the ejection faces of the heads to prevent the ink on and in the heads from drying. There may be cases where the heads need to be replaced because of their lives, trouble, etc.
FIGS. 20, 21A, 21B, 21C, 22A and 22B of the accompanying drawings show a known ink jet printer of the foregoing type. As shown in FIG. 20, the printer includes a carriage 103, a head holder 102 mounted removably on the carriage 103, and print heads 101 (only one shown) supported on the holder 102. Each head 101 has an ejection face 101a (FIGS. 22A and 22B) and an array of nozzles (not shown) formed in it. The front ends of the nozzles are open in the ejection face 101a. The holder 102 includes a pair of side walls 107. The carriage 103 includes a pair of side walls 106. The printer also includes protective caps 105 each for covering one of the ejection faces 101a. The caps 105 are positioned outside one edge of the path along which a printing medium moves. The caps 105 are supported at a fixed position, but with such slight play that they can incline forward and backward for close contact with the ejection faces 101a. 
The printer includes mounting mechanism 104 provided between the head holder 102 and the carriage 103 to mount the holder on the carriage. The mounting mechanism 104 include a pair of grooves 106a each formed on the inner side of one of the carriage walls 106. The front end of each groove 106a is closed, and the rear end is open and wider than the front end. The mounting mechanism 104 also include a pair of horizontal pins 107a each formed on one of the holder walls 107 to engage slidably with the adjacent groove 106a. 
It is possible to mount the head holder 102 on the carriage 103 by:
moving the holder 102 toward the protective caps 105, as shown in FIGS. 21A and 21B, with the holder pins 107a engaged with the carriage grooves 106a; and
then turning the holder 102 around its pins 107a clockwise in FIGS. 21A and 21B to bring the print heads 101 to the normal position shown in FIG. 21C, where the heads correctly face the printing position on the printing medium.
One might consider replacing the print heads 101 after moving the carriage 103 to a position where it faces the printing medium path. In such a case, it would be necessary to put the head holder 102 on the carriage 103 in a direction inclined with respect to the medium path, in such a manner that the upper edges of the heads 101 might move toward the medium path beyond the normal position of the heads 101. It would then be necessary to turn the inclined holder 102 to its normal position. When the upper edges of the heads 101 move toward the medium path, however, they would impinge on the printing medium, because the ejection faces 101a are normally spaced only about 2 mm from the path. It would consequently be impossible to replace the heads 101 when the carriage 103 faces the medium path.
Therefore, the print heads 101 can be replaced at their position where their ejection faces 101a are covered with the protective caps 105. The head replacement involves:
removing the head holder 102 from the carriage 103;
providing a new head holder 102 supporting new print heads 101;
engaging the horizontal pins 107a of the new holder 102 with the carriage grooves 106a, as shown in FIG. 22A, with the heads 101 inclined with respect to their normal position;
then moving the holder 102 until a portion over the ejection face 101a of each head 101 comes into contact with the upper edge of the associated protective cap 105;
further moving the holder 102, as shown in FIG. 22B, so that each cap 105 inclines around its upper edge and parallels the associated ejection face 101a; and
then turning the holder 102 around the pins 107a clockwise in FIGS. 22A and 22B to bring the heads 101 into the normal position, moving the ejection faces 101a upward.
When the ejection faces 101a move up, the caps 105, which are supported at their fixed position, rub on the faces. This may force dust etc. on the caps 105 and the ejection faces 101a into the head nozzles. Therefore, there is need for strong purging every time the heads 101 have been replaced. There may be cases where such purging is not sufficient to remove dust etc.
It is an object of the invention to provide an ink jet printer of which the print head can be replaced without the protective cap rubbing on the ejection face of the head.
In accordance with a first aspect of the invention, a printer is provided, which includes a carriage movable in opposite reciprocating directions. The carriage has a turning axis extending in the reciprocating directions. A head holder can be mounted on the carriage, and holds a print head. The head has an ejection face and a nozzle for ejecting ink onto a printing medium. The nozzle is open in the ejection face. The printer also includes a capping mechanism, which includes a protective cap for covering the ejection face. The head holder can be mounted on the carriage with a mounting mechanism by a process including the steps of:
moving the holder toward the turning axis until part of the holder arrives at the axis and until the ejection face comes into contact with the protective cap; and
thereafter turning the head holder around the axis.
The protective cap is supported in such a manner:
that, while out of contact with the ejection face, the cap is oriented opposite the direction in which the head holder can be moved toward the turning axis; and
that, while the holder is turned, the cap can turn in the turning directions in which the holder turns.
As stated above, the protective cap of this printer is supported in such a manner that, while it is out of contact with the ejection face, that is to say, while the head holder is not mounted on the carriage, the cap is oriented opposite the direction in which the head holder can be moved toward the turning axis. For replacement of the print head, a new head holder holding a new print head is first moved to the turning axis until part of the holder engages with the carriage. When the holder part engages with the carriage, the ejection face of this head faces and comes into close contact with the cap, as shown in FIG. 9B of the accompanying drawings. Subsequently, while the head holder is turned around the axis, the protective cap is turned, kept in contact with the ejection face. Therefore, while the head holder is turned, the protective cap does not slide on the ejection face. This prevents the nozzle from clogging due to the cap slide or slip.
In particular, the capping mechanism of this printer may be so designed that, when the print head is replaced, the front edge of the protective cap can follow the locus of the ejection face moving while the head holder is turning around the turning axis.
The capping mechanism may also include a casing. A cap holder for holding the protective cap may be supported by the casing movably in the turning directions. An urging member may be interposed between the casing and the cap holder. The member urges the protective cap to either a first position where the cap is oriented opposite the direction in which the head holder can be moved toward the turning axis or a second position where the cap faces the ejection face of the print head when the head holder has been mounted on the carriage.
The urging member can alternatively orient the protective cap. Specifically, the cap is oriented to the first position while the head holder is moving toward the cap perpendicularly to the turning axis, and to the second position when this holder has turned around the axis. This enables the protective cap to follow the turning ejection face of the print head.
The casing of the capping mechanism and the cap holder may be connected by a link mechanism. The cap holder may include a protrusion formed on it. The capping mechanism may further include a limiter for engaging with the protrusion to limit the movement of the protrusion.
In accordance with a second aspect of the invention, another printer is provided, which includes a carriage movable in opposite reciprocating directions. The carriage has a turning axis extending in the reciprocating directions. A head holder can be mounted on the carriage, and holds a print head. The head has an ejection face and a nozzle for ejecting ink onto a printing medium. The nozzle is open in the ejection face. The printer also includes a capping mechanism, which includes a protective cap for covering the ejection face. The printer further includes a mounting device. This device includes a guide, a turning mechanism and a locking mechanism. The guide can guide the head holder in a direction inclined with respect to the mounting position until part of the head holder arrives at the turning axis. The turning mechanism enables the guided holder to turn around the axis to the mounting position. The locking mechanism can lock the head holder at the mounting position. The protective cap can move between a first position where the cap is oriented opposite the inclined direction and a second position where the cap faces the print head when the head holder is at the mounting position. The protective cap is supported in such a manner that, while it is moving from the first position to the second position, it is in close contact with the ejection face of the print head.
While the head holder of this printer is turning around the turning axis, the protective cap can move from the first position to the second position, kept in close contact with the ejection face of the print head. That is to say, while the cap is moving from the first position to the second position, it does not slide on the ejection face. This prevents the nozzle from clogging due to the cap slide.
In accordance with a third aspect of the invention, still another printer is provided, which includes a carriage movable in opposite reciprocating directions. The carriage has a turning axis extending in the reciprocating directions. A head holder can be mounted on the carriage, and holds a print head. The head has an ejection face and a nozzle for ejecting ink onto a printing medium. The nozzle is open in the ejection face. The printer also includes a capping mechanism, which includes a protective cap for covering the ejection face. The printer further includes a mounting mechanism, with which the head holder can be mounted on the carriage by a process including the steps of: moving the head holder toward the turning axis until part of the holder arrives at the axis; and thereafter turning the head holder around the axis.
The protective cap is supported in such a manner:
that, when the head holder is moved toward the turning axis, the ejection face of the print head comes into contact with an edge of the cap; and
that, when the holder is turned around the axis, the ejection face and the cap come into close contact with each other without sliding on each other.
While the print head of this printer is replaced, the protective cap does not slide on the ejection face of the head. This prevents the nozzle from clogging.
In particular, the capping mechanism may be so designed that, while the head holder is turning around the turning axis, the edge of the cap and the line or the area on the ejection face which is in contact with the cap edge turn along the same locus.
The capping mechanism of this printer may further include a casing and a cap holder, which holds the protective cap. The cap holder is supported by the casing movably in the turning directions in which the head holder can turn. An urging member is interposed between the casing and the cap holder to urge the cap holder toward the print head. The casing, the cap holder and the urging member may be so designed that, while the head holder is turning around the turning axis, the edge of the cap and the line or the area on the ejection face which is in contact with the cap edge turn along the same locus.
The casing of this capping mechanism may include a back wall. The cap holder may include a pair of legs extending opposite the protective cap through the back wall. The legs are spaced in the turning directions, and may differ in length. The legs each have a stopper at the free end thereof for engaging with the back wall to limit the movement of the cap holder toward the print head.
The longer leg may be positioned on the leading side in the direction in which the head holder turns around the turning axis to be mounted on the carriage. The shorter leg may be positioned on the trailing side in this direction. In this case, the cap holder can move a longer distance on the leading side than on the trailing side.
The legs different in length and the urging member may be replaced with a pair of springs different in length as shown in FIG. 19A.
In accordance with a fourth aspect of the invention, yet another printer is provided, which includes a carriage. A head holder for holding a print head can be mounted on the carriage. The head has an ejection face and a nozzle for ejecting ink onto a printing medium. The nozzle is open in the ejection face. The printer also includes a capping mechanism, which includes a protective cap for covering the ejection face at a capping position where the cap faces the ejection face. The carriage can move in opposite reciprocating directions between a printing area where the carriage faces the printing medium and a capping area where the carriage faces the capping mechanism. The printer further includes a carriage controller for moving the carriage in the capping area to move the protective cap to a replacing position off the capping position when the head holder is to be mounted on the carriage.
When the print head of this printer is to be replaced, the controller moves the carriage in the capping area to move the protective cap to the replacing position which is offset from the capping position. The protective cap at the replacing position does not interfere with the ejection face of the print head while the head holder is mounted on the carriage.
The print head of this printer may comprise sub-heads arranged in the reciprocating directions. The protective cap may comprise sub-caps each associated with one of the sub-heads. The sub-heads may be displaced in the reciprocating directions from the sub-caps at the replacing position so that the sub-caps may not interfere with the sub-heads.
The carriage of this printer may have a turning axis extending in the reciprocating directions. The head holder may be mounted on the carriage by a process including the steps of: moving the head holder toward the turning axis until part of the holder arrives at the axis; and thereafter turning the holder around the axis.
In a conventional printer of this type, the head holder can be mounted on the carriage by such a process, with the protective caps kept at their capping position where they face the ejection faces of the print heads. While the head holder turns, the protective caps interfere with the ejection faces.
In accordance with the fourth aspect of the invention, the protective cap is at the replacing position offset from the capping position while the head holder is turning around the turning axis. The cap at the replacing position is out of contact with the ejection face while the head holder is turning.
The printer according to this aspect may further include a mounting mechanism with which the head holder can be mounted on the carriage. This mechanism may include a protrusion on at least one side of the head holder, a support in or on the carriage by which the protrusion can be supported rotatably, and a guide in or on the carriage for guiding the protrusion to the support.
This printer may further include a guide rod extending in the reciprocating directions. The carriage is supported slidably on the rod. The capping mechanism may further include a frame having a slope inclined with respect to the rod. The frame may support a guide shaft between the slope and the rod. The shaft extends in parallel with the rod. The protective cap may be supported by a casing, which is supported rotatably on and slidably along the shaft. The casing may include a first part for engaging with the carriage and a second part for sliding on the slope. In this case, when the carriage moves to the capping area, the carriage engages with the first part of the casing. This slides the second part on the slope to turn the casing around the shaft so that the cap approaches the ejection face. The invention is particularly effective for a printer including a capping mechanism of such structure.
While the protective cap of this printer is at the replacing position, the cap may be outside the locus described by the ejection face of the print head when the head holder turns around the turning axis. While the cap is at this position, the head holder can be mounted on the carriage. This keeps the ejection face of the head out of contact with the cap while the head holder is turning. In this case, the printer may further include a controller for controlling the movement of the carriage. This controller may control the position of the carriage in such a manner that, when the head holder is to be mounted on the carriage, the protective cap is off the capping position.